late 13c., from Old French pissier "urinate" (12c.), from Vulgar Latin *pissiare, of imitative origin. To piss away (money, etc.) is from 1948. Related: Pissed; pissing. Pissing while (1550s) once meant "a short time."

He shall not piss my money against the wall; he shall not have my money to spend in liquor. [Grose, "Classical Dictionary of the Vulgar Tongue," 3rd edition, 1796]

late 14c., from piss (v.). As a pure intensifier (piss-poor, piss-ugly, etc.) it dates from World War II. Piss and vinegar first attested 1942. Piss-prophet "one who diagnosed diseases by inspection of urine" is attested from 1620s. Piss proud "erect upon awakening" is attested from 1796.